To investigate the contamination characteristics of ultrafine particles
and gases originating from vehicle exhaust, data were obtained from one-week
intensive monitoring at an urban site in Seoul, Korea during the winter of 2003.
The diurnal variations of size-segregated particle concentrations for both
ultrafine particles (20&#8211;100 nm) and accumulation mode particles (100&#8211;600 nm)
were very similar. Strong morning peaks and weaker evening peaks of ultrafine
particles and NOx were observed at the site. The NOx concentration closely
followed the trend of ultrafine particle concentration, resulting in a high
determination coefficient (R2 = 0.65) for the relationship between these two
pollutants. When the wind conditions were favourable for the transport of
the air pollutants from busy neighbouring roads to the monitoring site, the
frequency of simultaneous observations was increased. Both ultrafine particles
and NOx were determined to be good indicators of the transport of vehicle
emissions from roads to urban surroundings.